Block Off Plate Code Chapter?

[jtp10181]

Can someone tell me the exact chapter and section # that talks about the block off plate stuff everyone is always talking about. I have NFPA 211 and NFPA 54 that I got a few months ago. I think they were either 2006 or 2007 versions. I want to read about it so I can be fully educated. Thanks.

 

[webbie]

I have never seen such a passage, however this is certainly covered in a lot of areas including many owners manuals. The lack of a block-off plate in most installations would result in an installation that allows excess air to flow up the chimney. However, if we read the letter of the code or manual in most of these cases, all that is required is that the installation be "sealed". In theory, this means a seal at the top or a seal at the fireplace front meets those specs. However, our shop has been installing such plates for 25+ years and we would do it no other way. It is quite simply the easiest way to get a tight seal, not allow excess room air up the chimney, and also not make the chimney part of the room (a chimney top seal does this).

So if the question is "Is a block off plate at the damper required by code?", I would say it is not. BUT, it is a better way to do things.

 

[BrotherBart]

The chatter is based on NFPA211 2006 12.4.5.1 (8). Which, by the way, is why insert manufacturers say they are only required with direct connects, not full liners.

Ball's in your court Elk.

 

[BrotherBart]

I have never seen such a passage, however this is certainly covered in a lot of areas including many owners manuals. The lack of a block-off plate in most installations would result in an installation that allows excess air to flow up the chimney. However, if we read the letter of the code or manual in most of these cases, all that is required is that the installation be "sealed". In theory, this means a seal at the top or a seal at the fireplace front meets those specs. However, our shop has been installing such plates for 25+ years and we would do it no other way. It is quite simply the easiest way to get a tight seal, not allow excess room air up the chimney, and also not make the chimney part of the room (a chimney top seal does this).

So if the question is "Is a block off plate at the damper required by code?", I would say it is not. BUT, it is a better way to do things.

Totally agree Craig on the use of one to keep the heat in the house and not going up into the bricks to be leached out to the outside. That is why I installed one with the hearth stove with liner but not the insert with liner that had a tightly sealed surround.

With the hearth stove it is also a good idea in case something breaches that liner. Ya don't want what the sealed top plate won't let out coming out into the living space. I think it is spelled CO.

 

[jtp10181]

I have also heard some people pack the top few feet with that non-combustible rock wool stuff. I would assume that is to keep the top few feet warm?

How do you all build these block off plates? Seems easiest would be to take two plates and cut a half circle. Enclose them around the vent and seal with HT silicone. How to attach it inside the flue? Masonry screws? Or do you just caulk it in? Or wedge it?

Now what about the surround on the unit? Do you also seal that off or just leave it be since the block off plate pretty much takes care of everything.

If everyone does not already know I work at a dealer... I am the field supervisor. I have only been there almost 3 years and I am slowly finding and correcting things that have been done sub-par for many many years. I only wish I could go back to every single customer and retrofit them with our current standards but I can only do so much. Our company is all about going above and beyond code and install requirements to give the customer the best hearth experience they can find anywhere in the area.

 

[Shane]

Measure the Backwall Width. Measure the front inside width. Measure Depth. Cut sheet metal to appropriate size with 1" tabs. Fold tabs over with brake or handseamer. INstall liner measure distance from back wall when in final resting position. Cut hole. Install plate drop liner.
Basic breakdown a more detailed article is in the how to section.

 

[webbie]

Here are all the secrets -
https://www.hearth.com/econtent/index.php/articles/making_a_block_off_plate/

 

[elkimmeg]

2006 direct cut and paste

RESIDENTIAL
CODE®
FOR ONE- AND TWO-FAMILY DWELLINGS

Part V — Mechanical
CHAPTER 18 Chimney& Vents
MECHANICAL

M1803.4 Connection to fireplace flue. Connection of appliances
to chimney flues serving fireplaces shall comply with
Sections M1803.4.1 through M1803.4.4.

M1803.4.1 Closure and accessibility. A rigid noncombustible
seal shall be provided below the point of connection to prevent
entry of room air into the flue. Means shall be provided
for access to the flue for inspection and cleaning

 

[jtp10181]

So technically people can get away with sealing it at the surround... IMO that is a joke. I will get my guys with the program ASAP after I talk to the store manager. I don't remeber the units we install even coming with insulation on the surround panel. I know the gas inserts do but I don't think the wood ones do.

 

[elkimmeg]

I will not pass an installation without a block off plate. What happens with common insulation for one Fiv berglass is not a tested and approved use plus it is not made for that heat range In summer in humidity the insulation gathers moisture and saggs and shifts it no longer affords a seal

Then there is code governing intrusion of room air

Someone mentioned RTV caulk well that is ok around the permimeter But does not satisy the heat range sealing the plate and connector pipe here is where I require 1200 or more
draft sealant or gasket cement I suggers yo look into Copperfields they have premade block off plates where they use a bracket and a wing nut and tighten the wing nut that applies pressure to hold the plate in place Another common way is to use tap corns for concrete fastening or sheet metal screws to the damper frame.

Rock wool may have the temp range but it will soak in condensation moisture and does not satisfy rdgidity. However not a bad idea to pack in in above the damper

I'm glad tou have the NFPA211 but it is not reconixed as a national body of code the International code is the reconized code

 

[BrotherBart]

2006 direct cut and paste

RESIDENTIAL
CODE®
FOR ONE- AND TWO-FAMILY DWELLINGS

Part V — Mechanical
CHAPTER 18 Chimney& Vents
MECHANICAL

M1803.4 Connection to fireplace flue. Connection of appliances
to chimney flues serving fireplaces shall comply with
Sections M1803.4.1 through M1803.4.4.

M1803.4.1 Closure and accessibility. A rigid noncombustible
seal shall be provided below the point of connection to prevent
entry of room air into the flue. Means shall be provided
for access to the flue for inspection and cleaning

When the full liner is connected to the stove/insert it IS the flue. The rest is just a bunch of bricks aimed at the sky that keep the rain off of the liner and holds up the top plate and chimney cap. :cheese:

According to that wording a rigid noncombustble seal has to be provided below the connection point of the liner to the stove.

There ain't no code that requires a block off plate on an insert with a full liner.

 

[philaphire]

I'm no lawyer, but BroBart seems to be reading the code correctly if you ask me. Seems that the code clearly implies a block off plate is only necessary when direct connects are used. If the point is (to quote the quote) "to prevent entry of room air into the flue" then in the case of a full reline merely having your stove door closed would suffice.

 

[GVA]

jtp here's some old reading.
EDIT*****sorry it didn't post the first time...
https://www.hearth.com/talk/threads/6043/

I'm no expert on this but what do you think about this install? And symptoms?
It may be what you are talking about, maybe not..........

I'm bored..........Where are all the pellet problems and noises..............I'm ducking now


And what ever happend to county lady........
I wonder what she found?????

 

[elkimmeg]

There ain’t no code that requires a block off plate on an insert with a full liner.

Slow time of the year for you been about 4 monthes since you posted the same question or made the same statement

I get tired re-posting the same arguement over and over. Lets say there is enough code language for me to require them

whats wrong with creating a dead aie space I believe it has an insulation value? What is the r-value of a single 24 gage sheetmetal
I will save you the effort almost nothing so warm air entering the chimney rising heat will transfere threw that 24 gage roof cap readilly
with very little resistance With a dead air space heat from the living space never makes it that far

My question to you is the installation better with a block off plate?

 

[rdrcr56]

How come on an insert install with a full liner you can seal the top of the existing masonry flue, but on a stove install with a framed in chase the top plate has to have 1/2 in. gap to allow air flow to prevent condensation? Seem's like the same thing to me.

 

[Harley]

Don't know why, but it made me think about this thread from a little while back. Based on the theory that the seal up top where the liner comes out counts as a block off plate - would it mean that there is 3 block off's in this situation? In any event - I do believe the "2nd" did make a difference, so whether its required by code or not, I think the dead air spase created is certainly going to help the stove get more heat into the rooms, rather than going up the flue.

https://www.hearth.com/talk/threads/5580/

 

[elkimmeg]

point of connection id the point where connector pipe enter the flue area. That's right common connector pipe can be used up to the point of connection is, once it enters the throat chamber of the chimney. Laymen terms it can not pass beyond the damper area. Beyond the damper which it the chimney entrance it must be stailless steel it is ok to use the liner to the stove outlet but the point of connection is the Damper passage. Just below it would be where a ridgid non combustiable seal is required. Ie t a damper plate. No lawer needed just the comentary of the international mechanical codes

 

[TruePatriot]

Elk and Everyone,

How are you?

Interesting reading on block off plates, as we will need one, to use our existing, outside, masonry chimney. We plan to have a hole cut into the chimney, over our fireplace, inside, and hook up a wood stove that way, after the chimney is inspected and lined with a 6" stainless liner, of course.

To save some $ and because I enjoy working with metal, I'd like to make my own blockoff plate. I printed Craig's Wiki on this topic but haven't read it yet. In scanning it, however, I didn't see where the gauge of steel required was given.

Is there a requirement for what gauge steel should be used?

If no requirement, what is a good balance, between "thick enough" and "too stiff to work with?"

I'm thinking I should use galvanized steel, as condesnsation is likely to promote rust. Is there any problem with this?

I saw you recommended "Tap Cons" to affix the plate in the damper area, or possibly sheet metal screws into the damper frame, so I may use a combination of same. I plan to try to set the Tap Cons into the morter between the bricks, where the drillin' is easier, unless there is a reason not to?

Since we will not be running a flue through the block off plate (as we're cutting in above the mantel piece of the fireplace) can you recommend what type of sealant I can use around the edge of the block off plate? I've heard of "high temp. RTV" but can you be more specific?

Thanks in advance.

Peter

 

[elkimmeg]

Tap cons in the motar joint works I think Home cheapo sells 2/2 sheets of Galv steel. 24 gage seems to do the trick and is workable.
one also could get by with 26 gage

They may even sell RTV caulk in the HVAC section, it is good for up to 500/ 600 degrees and will work fine

Tp what did you end up purchasing for your stove?

 

[webbie]

Although it sounds crude, we always used masonry nails in the mortar joints and drove them part way in. The secret was holding them with a pliers while you hit them. Keep in mind that our plates has a 1" ledge and we had to beat them in place, so they would not move even without the nails. The nails functioned as "pins" only and were easily removed and reinstalled over the years. Tapcons were not very popular back in 1979 when we started doing this!

We always use silicone around the plate and usually put furnace cement (if possible) around where the pipe goes through.

I guess Elk put the code issue to rest. This shows the folly of following owners manuals.......which is troubling. We looked at a bunch of manuals in one earlier thread and they had drawings that did not show a bottom plate as well as text descriptions that mentioned that just a seal at the front or top (somewhere) was needed.

I guess this is one of those situations that a customer can measure a dealer by.

Actually, reading the code, it would seem as if a well sealed front plate would suffice - because that is below the point of connection (in a manner of speaking).

 

[TMonter]

M1803.4.1 Closure and accessibility. A rigid noncombustible
seal shall be provided below the point of connection to prevent
entry of room air into the flue. Means shall be provided
for access to the flue for inspection and cleaning

It sounds to me as if this means if you are doing a complete reline you wouldn't need a block-off plate. At that point the flue is the liner so as long as the liner meets the code for fire rating with 1/2" of insulation, you'd be in the clear. With a complete liner there is no way for room air to enter the flue provided the flue is sealed off at the top. In either case the code isn't very clear especially when it comes to relines. I didn't use a block-off plate on mine, instead I packed the space between the liner and old flue with 2500 degree block insulation.

 

[webbie]

Yeah, one could read code like the bible....

On one hand it says "A rigid noncombustible
seal shall be provided below the point of connection"

On the other hand, it says "to prevent
entry of room air into the flue"

So the reasoning is to prevent room air from entering the flue? If so, a top seal does the same thing. I guess it is like anything else - you have to work with that you have, and make field decisions...and there is, as usual, the good, better and best way of doing it.

My opinion would be that all hearth stove (without front plates, etc.) should have the damper metal seal - whether lined or not. If an insert has a decent front sealing plate and is fully lined...well, that would seem to be more optional.